Voltage converters such as DC-DC converters come in two forms. When an input voltage is to be stepped up in voltage by the converter, a boost or step-up configuration is provided. When the input voltage needs to be stepped down to a lower voltage by the converter, a buck converter is provided. Thus, a buck converter is a step-down DC-DC converter. Its design is similar to the step-up boost converter, and like the boost converter, it is a switched-mode power supply that employs switches (e.g., a transistor and a diode), an inductor and a capacitor. The most straight-forward manner to reduce the voltage of a DC supply is to use a linear regulator, but linear regulators waste energy as they operate by dissipating excess power as heat. Switching converters such as buck converters, on the other hand, can be remarkably efficient (95% or higher for integrated circuits), making them useful for tasks such as converting the main voltage in a computer (e.g., 12 V in a desktop, 12-24 V in a laptop) down to the 0.8-1.8 volts needed by the processor.
Another type of step-down or buck converter is a multiphase converter which is used to address high load current situations. By using two inductors in parallel to generate the output voltage instead of a single inductor, designers can reduce input and output ripple as well as mitigate inductor power losses while increasing the load transient response of the converter. When two inductors are employed as opposed to single inductor designs, two parallel paths within driving circuitry need to be maintained thus requiring some type of current balancing between the paths. To realize additional current balancing, means must be provided to measure current flowing through each inductor. Sensing current in a switching converter is not very practical, however, since it is not possible for a single device to monitor continuous load current and across which a DC sense device could be operated effectively. Methods for sampling a voltage on a replica stage power FET to determine loop currents are sometimes employed, yet such techniques are inaccurate, noise sensitive, and slow, thus limiting performance of the overall current balancing loop.